This commit implements David Rientjes' idea of mempressure cgroup.
The main characteristics are the same to what I've tried to add to vmevent API; internally, it uses Mel Gorman's idea of scanned/reclaimed ratio for pressure index calculation. But we don't expose the index to the userland. Instead, there are three levels of the pressure:
o low (just reclaiming, e.g. caches are draining); o medium (allocation cost becomes high, e.g. swapping); o oom (about to oom very soon).
The rationale behind exposing levels and not the raw pressure index described here: http://lkml.org/lkml/2012/11/16/675
For a task it is possible to be in both cpusets, memcg and mempressure cgroups, so by rearranging the tasks it is possible to watch a specific pressure (i.e. caused by cpuset and/or memcg).
Note that while this adds the cgroups support, the code is well separated and eventually we might add a lightweight, non-cgroups API, i.e. vmevent. But this is another story.
Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org --- Documentation/cgroups/mempressure.txt | 50 ++++++ include/linux/cgroup_subsys.h | 6 + include/linux/vmstat.h | 11 ++ init/Kconfig | 12 ++ mm/Makefile | 1 + mm/mempressure.c | 330 ++++++++++++++++++++++++++++++++++ mm/vmscan.c | 4 + 7 files changed, 414 insertions(+) create mode 100644 Documentation/cgroups/mempressure.txt create mode 100644 mm/mempressure.c
diff --git a/Documentation/cgroups/mempressure.txt b/Documentation/cgroups/mempressure.txt new file mode 100644 index 0000000..dbc0aca --- /dev/null +++ b/Documentation/cgroups/mempressure.txt @@ -0,0 +1,50 @@ + Memory pressure cgroup +~~~~~~~~~~~~~~~~~~~~~~~~~~ + Before using the mempressure cgroup, make sure you have it mounted: + + # cd /sys/fs/cgroup/ + # mkdir mempressure + # mount -t cgroup cgroup ./mempressure -o mempressure + + It is possible to combine cgroups, for example you can mount memory + (memcg) and mempressure cgroups together: + + # mount -t cgroup cgroup ./mempressure -o memory,mempressure + + That way the reported pressure will honour memory cgroup limits. The + same goes for cpusets. + + After the hierarchy is mounted, you can use the following API: + + /sys/fs/cgroup/.../mempressure.level +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + To maintain the interactivity/memory allocation cost, one can use the + pressure level notifications, and the levels are defined like this: + + The "low" level means that the system is reclaiming memory for new + allocations. Monitoring reclaiming activity might be useful for + maintaining overall system's cache level. Upon notification, the program + (typically "Activity Manager") might analyze vmstat and act in advance + (i.e. prematurely shutdown unimportant services). + + The "medium" level means that the system is experiencing medium memory + pressure, there is some mild swapping activity. Upon this event + applications may decide to free any resources that can be easily + reconstructed or re-read from a disk. + + The "oom" level means that the system is actively thrashing, it is about + to out of memory (OOM) or even the in-kernel OOM killer is on its way to + trigger. Applications should do whatever they can to help the system. + + Event control: + Is used to setup an eventfd with a level threshold. The argument to + the event control specifies the level threshold. + Read: + Reads mempory presure levels: low, medium or oom. + Write: + Not implemented. + Test: + To set up a notification: + + # cgroup_event_listener ./mempressure.level low + ("low", "medium", "oom" are permitted.) diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h index f204a7a..b9802e2 100644 --- a/include/linux/cgroup_subsys.h +++ b/include/linux/cgroup_subsys.h @@ -37,6 +37,12 @@ SUBSYS(mem_cgroup)
/* */
+#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_MEMPRESSURE) +SUBSYS(mpc_cgroup) +#endif + +/* */ + #if IS_SUBSYS_ENABLED(CONFIG_CGROUP_DEVICE) SUBSYS(devices) #endif diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h index a13291f..c1a66c7 100644 --- a/include/linux/vmstat.h +++ b/include/linux/vmstat.h @@ -10,6 +10,17 @@
extern int sysctl_stat_interval;
+struct mem_cgroup; +#ifdef CONFIG_CGROUP_MEMPRESSURE +extern void vmpressure(struct mem_cgroup *memcg, + ulong scanned, ulong reclaimed); +extern void vmpressure_prio(struct mem_cgroup *memcg, int prio); +#else +static inline void vmpressure(struct mem_cgroup *memcg, + ulong scanned, ulong reclaimed) {} +static inline void vmpressure_prio(struct mem_cgroup *memcg, int prio) {} +#endif + #ifdef CONFIG_VM_EVENT_COUNTERS /* * Light weight per cpu counter implementation. diff --git a/init/Kconfig b/init/Kconfig index 7d30240..d526249 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -891,6 +891,18 @@ config MEMCG_KMEM the kmem extension can use it to guarantee that no group of processes will ever exhaust kernel resources alone.
+config CGROUP_MEMPRESSURE + bool "Memory pressure monitor for Control Groups" + help + The memory pressure monitor cgroup provides a facility for + userland programs so that they could easily assist the kernel + with the memory management. So far the API provides simple, + levels-based memory pressure notifications. + + For more information see Documentation/cgroups/mempressure.txt + + If unsure, say N. + config CGROUP_HUGETLB bool "HugeTLB Resource Controller for Control Groups" depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL diff --git a/mm/Makefile b/mm/Makefile index 3a46287..e69bbda 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -51,6 +51,7 @@ obj-$(CONFIG_MIGRATION) += migrate.o obj-$(CONFIG_QUICKLIST) += quicklist.o obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o obj-$(CONFIG_MEMCG) += memcontrol.o page_cgroup.o +obj-$(CONFIG_CGROUP_MEMPRESSURE) += mempressure.o obj-$(CONFIG_CGROUP_HUGETLB) += hugetlb_cgroup.o obj-$(CONFIG_MEMORY_FAILURE) += memory-failure.o obj-$(CONFIG_HWPOISON_INJECT) += hwpoison-inject.o diff --git a/mm/mempressure.c b/mm/mempressure.c new file mode 100644 index 0000000..ea312bb --- /dev/null +++ b/mm/mempressure.c @@ -0,0 +1,330 @@ +/* + * Linux VM pressure + * + * Copyright 2012 Linaro Ltd. + * Anton Vorontsov anton.vorontsov@linaro.org + * + * Based on ideas from Andrew Morton, David Rientjes, KOSAKI Motohiro, + * Leonid Moiseichuk, Mel Gorman, Minchan Kim and Pekka Enberg. + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 as published + * by the Free Software Foundation. + */ + +#include <linux/cgroup.h> +#include <linux/fs.h> +#include <linux/sched.h> +#include <linux/mm.h> +#include <linux/vmstat.h> +#include <linux/eventfd.h> +#include <linux/swap.h> +#include <linux/printk.h> + +static void mpc_vmpressure(struct mem_cgroup *memcg, ulong s, ulong r); + +/* + * Generic VM Pressure routines (no cgroups or any other API details) + */ + +/* + * The window size is the number of scanned pages before we try to analyze + * the scanned/reclaimed ratio (or difference). + * + * It is used as a rate-limit tunable for the "low" level notification, + * and for averaging medium/oom levels. Using small window sizes can cause + * lot of false positives, but too big window size will delay the + * notifications. + */ +static const uint vmpressure_win = SWAP_CLUSTER_MAX * 16; +static const uint vmpressure_level_med = 60; +static const uint vmpressure_level_oom = 99; +static const uint vmpressure_level_oom_prio = 4; + +enum vmpressure_levels { + VMPRESSURE_LOW = 0, + VMPRESSURE_MEDIUM, + VMPRESSURE_OOM, + VMPRESSURE_NUM_LEVELS, +}; + +static const char *vmpressure_str_levels[] = { + [VMPRESSURE_LOW] = "low", + [VMPRESSURE_MEDIUM] = "medium", + [VMPRESSURE_OOM] = "oom", +}; + +static enum vmpressure_levels vmpressure_level(uint pressure) +{ + if (pressure >= vmpressure_level_oom) + return VMPRESSURE_OOM; + else if (pressure >= vmpressure_level_med) + return VMPRESSURE_MEDIUM; + return VMPRESSURE_LOW; +} + +static ulong vmpressure_calc_level(uint win, uint s, uint r) +{ + ulong p; + + if (!s) + return 0; + + /* + * We calculate the ratio (in percents) of how many pages were + * scanned vs. reclaimed in a given time frame (window). Note that + * time is in VM reclaimer's "ticks", i.e. number of pages + * scanned. This makes it possible to set desired reaction time + * and serves as a ratelimit. + */ + p = win - (r * win / s); + p = p * 100 / win; + + pr_debug("%s: %3lu (s: %6u r: %6u)\n", __func__, p, s, r); + + return vmpressure_level(p); +} + +void vmpressure(struct mem_cgroup *memcg, ulong scanned, ulong reclaimed) +{ + if (!scanned) + return; + mpc_vmpressure(memcg, scanned, reclaimed); +} + +void vmpressure_prio(struct mem_cgroup *memcg, int prio) +{ + if (prio > vmpressure_level_oom_prio) + return; + + /* OK, the prio is below the threshold, send the pre-OOM event. */ + vmpressure(memcg, vmpressure_win, 0); +} + +/* + * Memory pressure cgroup code + */ + +struct mpc_event { + struct eventfd_ctx *efd; + enum vmpressure_levels level; + struct list_head node; +}; + +struct mpc_state { + struct cgroup_subsys_state css; + + uint scanned; + uint reclaimed; + struct mutex sr_lock; + + struct list_head events; + struct mutex events_lock; + + struct work_struct work; +}; + +static struct mpc_state *wk2mpc(struct work_struct *wk) +{ + return container_of(wk, struct mpc_state, work); +} + +static struct mpc_state *css2mpc(struct cgroup_subsys_state *css) +{ + return container_of(css, struct mpc_state, css); +} + +static struct mpc_state *tsk2mpc(struct task_struct *tsk) +{ + return css2mpc(task_subsys_state(tsk, mpc_cgroup_subsys_id)); +} + +static struct mpc_state *cg2mpc(struct cgroup *cg) +{ + return css2mpc(cgroup_subsys_state(cg, mpc_cgroup_subsys_id)); +} + +static void mpc_event(struct mpc_state *mpc, ulong s, ulong r) +{ + struct mpc_event *ev; + int level = vmpressure_calc_level(vmpressure_win, s, r); + + mutex_lock(&mpc->events_lock); + + list_for_each_entry(ev, &mpc->events, node) { + if (level >= ev->level) + eventfd_signal(ev->efd, 1); + } + + mutex_unlock(&mpc->events_lock); +} + +static void mpc_vmpressure_wk_fn(struct work_struct *wk) +{ + struct mpc_state *mpc = wk2mpc(wk); + ulong s; + ulong r; + + mutex_lock(&mpc->sr_lock); + s = mpc->scanned; + r = mpc->reclaimed; + mpc->scanned = 0; + mpc->reclaimed = 0; + mutex_unlock(&mpc->sr_lock); + + mpc_event(mpc, s, r); +} + +static void __mpc_vmpressure(struct mpc_state *mpc, ulong s, ulong r) +{ + mutex_lock(&mpc->sr_lock); + mpc->scanned += s; + mpc->reclaimed += r; + mutex_unlock(&mpc->sr_lock); + + if (s < vmpressure_win || work_pending(&mpc->work)) + return; + + schedule_work(&mpc->work); +} + +static void mpc_vmpressure(struct mem_cgroup *memcg, ulong s, ulong r) +{ + /* + * There are two options for implementing cgroup pressure + * notifications: + * + * - Store pressure counter atomically in the task struct. Upon + * hitting 'window' wake up a workqueue that will walk every + * task and sum per-thread pressure into cgroup pressure (to + * which the task belongs). The cons are obvious: bloats task + * struct, have to walk all processes and makes pressue less + * accurate (the window becomes per-thread); + * + * - Store pressure counters in per-cgroup state. This is easy and + * straightforward, and that's how we do things here. But this + * requires us to not put the vmpressure hooks into hotpath, + * since we have to grab some locks. + */ + +#ifdef CONFIG_MEMCG + if (memcg) { + struct cgroup_subsys_state *css = mem_cgroup_css(memcg); + struct cgroup *cg = css->cgroup; + struct mpc_state *mpc = cg2mpc(cg); + + if (mpc) + __mpc_vmpressure(mpc, s, r); + return; + } +#endif + task_lock(current); + __mpc_vmpressure(tsk2mpc(current), s, r); + task_unlock(current); +} + +static struct cgroup_subsys_state *mpc_css_alloc(struct cgroup *cg) +{ + struct mpc_state *mpc; + + mpc = kzalloc(sizeof(*mpc), GFP_KERNEL); + if (!mpc) + return ERR_PTR(-ENOMEM); + + mutex_init(&mpc->sr_lock); + mutex_init(&mpc->events_lock); + INIT_LIST_HEAD(&mpc->events); + INIT_WORK(&mpc->work, mpc_vmpressure_wk_fn); + + return &mpc->css; +} + +static void mpc_css_free(struct cgroup *cg) +{ + struct mpc_state *mpc = cg2mpc(cg); + + kfree(mpc); +} + +static ssize_t mpc_read_level(struct cgroup *cg, struct cftype *cft, + struct file *file, char __user *buf, + size_t sz, loff_t *ppos) +{ + struct mpc_state *mpc = cg2mpc(cg); + uint level; + const char *str; + + mutex_lock(&mpc->sr_lock); + + level = vmpressure_calc_level(vmpressure_win, + mpc->scanned, mpc->reclaimed); + + mutex_unlock(&mpc->sr_lock); + + str = vmpressure_str_levels[level]; + return simple_read_from_buffer(buf, sz, ppos, str, strlen(str)); +} + +static int mpc_register_level(struct cgroup *cg, struct cftype *cft, + struct eventfd_ctx *eventfd, const char *args) +{ + struct mpc_state *mpc = cg2mpc(cg); + struct mpc_event *ev; + int lvl; + + for (lvl = 0; lvl < VMPRESSURE_NUM_LEVELS; lvl++) { + if (!strcmp(vmpressure_str_levels[lvl], args)) + break; + } + + if (lvl >= VMPRESSURE_NUM_LEVELS) + return -EINVAL; + + ev = kzalloc(sizeof(*ev), GFP_KERNEL); + if (!ev) + return -ENOMEM; + + ev->efd = eventfd; + ev->level = lvl; + + mutex_lock(&mpc->events_lock); + list_add(&ev->node, &mpc->events); + mutex_unlock(&mpc->events_lock); + + return 0; +} + +static void mpc_unregister_level(struct cgroup *cg, struct cftype *cft, + struct eventfd_ctx *eventfd) +{ + struct mpc_state *mpc = cg2mpc(cg); + struct mpc_event *ev; + + mutex_lock(&mpc->events_lock); + list_for_each_entry(ev, &mpc->events, node) { + if (ev->efd != eventfd) + continue; + list_del(&ev->node); + kfree(ev); + break; + } + mutex_unlock(&mpc->events_lock); +} + +static struct cftype mpc_files[] = { + { + .name = "level", + .read = mpc_read_level, + .register_event = mpc_register_level, + .unregister_event = mpc_unregister_level, + }, + {}, +}; + +struct cgroup_subsys mpc_cgroup_subsys = { + .name = "mempressure", + .subsys_id = mpc_cgroup_subsys_id, + .css_alloc = mpc_css_alloc, + .css_free = mpc_css_free, + .base_cftypes = mpc_files, +}; diff --git a/mm/vmscan.c b/mm/vmscan.c index 16b42af..fed0e04 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1900,6 +1900,9 @@ restart: shrink_active_list(SWAP_CLUSTER_MAX, lruvec, sc, LRU_ACTIVE_ANON);
+ vmpressure(sc->target_mem_cgroup, + sc->nr_scanned - nr_scanned, nr_reclaimed); + /* reclaim/compaction might need reclaim to continue */ if (should_continue_reclaim(lruvec, nr_reclaimed, sc->nr_scanned - nr_scanned, sc)) @@ -2122,6 +2125,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist, count_vm_event(ALLOCSTALL);
do { + vmpressure_prio(sc->target_mem_cgroup, sc->priority); sc->nr_scanned = 0; aborted_reclaim = shrink_zones(zonelist, sc);